Influence of Sex and Age in the Risk of Urolithiasis—A Biochemical Evaluation in Indian Subjects

Abstract

SUMMARY. Urinary lithogenic promoters and inhibitors were estimated in normal Indian men and women of young and old ages to understand the sex difference in the risk of stone disease. Young men displayed increased phosphate excretion and a higher mean calcium (both lithogenic promoters) and lower excretion of citrate (lithogenic inhibitor) compared to women of the same age indicating that young men are more at risk for calculous disease than women. In the older postmenopausal women, there was increased excretion of calcium and magnesium and a lower mean citrate than in the younger women suggesting that oestrogenic activity during reproductive years appears to offer protection against calculogenesis. This study indicates that sex differences exist in the excretion of lithogenic promoters and inhibitors which partly explain the difference in the incidence of urolithiasis between men and women. Additional key phrases: urinanalysis; Iithogenic promoters and inhibitorsEpidemiological studies indicate that many factors like age, sex, industrialization, and socio-economic status influence urolithiasis.' The biochemical basis of the urinary stone disease, however, is not clearly understood. We have reported from this laboratory the incidence of urolithiasis in relation to age and sex: chemical analysis of urinary c a l c~l i~-~ and the relationship between the age of patients with stones and calculus c o m p~s i t i o n .~ The incidence of urolithiasis is much higher in men compared to Further, our findings indicate that the stone disease is higher in men compared to women at each age group and for each category of stones.2 The present study incorporates the data on certain urinary lithogenic promoters and inhibitors in young and old groups of men and women to evaluate biochemically the role of sex and age in the risk of urolithiasis. MATERIALS AND METHODSNormal and healthy young subjects (men n = 33, women n-28; mean age 26 years) and older Correspondence: Dr U Satyanarayana. subjects (men n=24, women n=24; mean ages 60 and 62 years, respectively) were selected for this study. All the older women were postmenopausal and untreated. All subjects were allowed to continue with their regular diet with normal activities. Twenty-four hour urine samples were collected from all subjects. There was no significant difference in the daily urine volumes among the four groups. Urine from each subject was distributed into two vials, one with hydrochloric acid (10 mmol) as preservative and samples were stored at -20 " C until analysed. Except for uric acid, which was estimated in urine samples free of preservative, the other substances were analysed in acid containing samples. Calcium was determined by the ortho-cresolphthalein method as described in Varleyl" and oxalate by Hodgkinson's procedure" while phosphate was estimated by the method described in Wootton and Freeman.12 Uric acid was estimated by the phosphotungstate method.13 Citrate was determined by a colorimetric p r~c e d u r e , '~ magnesium by the titan yellow method15 an...